From what I've read here I have been resizing incorrectly. My brass comes out of the rifle at 1.640, the bolt closes on a 1.638 case, the builder says its a 1.632 chamber, I've resizing to 1.630 per Zediker, is this why my last 1000 reloads suck?? I need to resize to only 1.638? thanks ahead of time!
sizing help
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Thanks! I measured with a RCBS which was calibrated with a 1.630 headspace gauge. I assumed that the chamber was 1.632 at one time, since that was what I was told, it had to of increased with the 1000 reloads? Anyway, I was sizing to 1.630, but after reading a few posts, I checked it and it comes out to 1.638, so I should size to 1.636 and go from there. This could explain what I see on paper is the back and forth groups that I assume is the mag tension on the bolt tossing the undersized case around in the chamber. This doesn't exlain why FGMM shoots .75" and mine shoot 1.5", being that their cases measure 1.628 alot of the time. But this could the phenonemon that Zediker explains that the new FG case is smaller diameter than my FL sized case and finds the oval part of the chamber more consistantly. I have small base dies as well, but they still do not size as small as a new FG case, and they didn't improve a thing. I have to believe there is something fundamentally flawed with my process, could this be it? Or am I talking out of my keister?
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Hmmm... why do you think your chamber size has changed? Throat yes but hardly significant. Chamber????
Well, the only thing I can think of is the smith who installed the barrel wasn't correct when he told me it was 1.632 military, when it was 1.638 all along. Now, the headspace gauges I have are Forster 308 gauges and this could be the difference? That I do not know. I don't think that would be this big of a difference. Of course we also realize that brass has more give to it than a steel gauge, so I imagine it could be slightly less than 1.638, the 1.638 gauge my friend has doesn't quite close by a hair, so 1.637 is probably closer.
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Why not do a cast of the chamber and know for sure?
http://www.brownells.com/aspx/NS/store/productdetail.aspx?p=384&st=chamber cast&s=
http://www.brownells.com/aspx/NS/store/productdetail.aspx?p=384&st=chamber cast&s=
I think you were hitting the shoulder back too far as you already surmised. Since you seem to know a bit about handloading, how do you process your fired brass' primer pockets? Are you using FGMM brass for your reloads? Now to my experience...I process my primer pockets with an RCBS case-mate. I deburr the inside of the flash-hole and uniform the primer pocket. I never use FGMM as reloads and rarely shoot them. I assure you that I am not an 'expert' but the proper preperation of the 'exit' side of the flash-hole and uniforming of the primer pocket itself will yield better results with any once-fired brass.
Thanks for the replies! I've used Win, Rem, Hertinberger, RA61, Federal, Hornady, LC brass for the load development. I have approx. 1500 cases of once fired federal, 3000 cases of RA61, and 1000 cases of Hertinberger. The rest are just samples for checking to see how they shoot. I've tried RCBS x-dies, full and small base, Forster benchrest Fl dies, and Redding small base with neck sizer, I use the Forster benchrest seater, it is excellent in terms of runout. I've tried 41g to 43g of Re15, Varget, 4064, I4895,H4896 in all the cases, my Chrono readings say that my sd and ad are slightly above 10 with sd around 16. I've stayed with sierra bullets, 168 and 175 with no real difference in groups. I uniform the primer pocket and debur the flashhole, I turn the case 1/3 of a turn when I am seating, and turn the case 1/2 turn when sizing. I also use the RCBS case mate to debur and chamfer, its excellent. I use Gold Medal Primers, and win primers. I weigh my cases. I weigh the charge, Have tried seating depth changes but seems to be happiest with 2.804. Its a Krieger heavy with 1-10, mcmillan stock, rader trigger, Wolf springs, Leopold 10X tactical scope, Arms 18, sadlak spring guide. Looking back into my notes it seems that Federal brass has been the most accurate, but I have alot of RA61 and it lasts longer, the federals loose the primer hold after 4 loadings, so my development as of late has revolved around these cases, and they seem to be of good quality. I'm doing something wrong, my standard wieght M1a shoots 1.5" with FGMM 168s all day with a crummy GI fiberglass stock, but I feel we might be on the right track with case sizing here, I will find out shortly when I head to the range with my latest batch, last night I sized Federal and Ra61 to 1.635, with the forsters and Redding dies. Thanks again!
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Sometimes all these gadgets cause you confusion.
My rifle came with a perfect rifle specific cartridge case gage.....it's chamber.
My method of late, take 10 cases, resize them long so the stripped bolt won't close on the clean sized case. Run the die down in small increments or even better use the Redding competition shell holder set. Resize until all go in the chamber and the bolt just closes without tension. Then go down .004 more. I can do this rapidly with the Redding set. I really don't need to know if they're 1.638 or 1.631, I need about .003-.004 of room for chambering, locking and expansion upon firing.
If you have more than one rifle you should segregate your ammo for each unless they have the same headspace.
Nut
if I'm off base someone fire up a flare
My rifle came with a perfect rifle specific cartridge case gage.....it's chamber.
My method of late, take 10 cases, resize them long so the stripped bolt won't close on the clean sized case. Run the die down in small increments or even better use the Redding competition shell holder set. Resize until all go in the chamber and the bolt just closes without tension. Then go down .004 more. I can do this rapidly with the Redding set. I really don't need to know if they're 1.638 or 1.631, I need about .003-.004 of room for chambering, locking and expansion upon firing.
If you have more than one rifle you should segregate your ammo for each unless they have the same headspace.
Nut
if I'm off base someone fire up a flare
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I used to turn off the gas cylinder spindle valve and "fire-size" my match brass. and manually extract it from the chamber after a few seconds of cool-down.
That was in the days when I shot local matches. I would then use the RCBS case measurement gauge to get a numerical idea of my chamber dimensions and adjust my sizing die accordingly. Worked ok for my level of (non) proficiency
Sizing and/or measuring off an automatically-extracted case won't give you an accurate picture of the chamber due to the extremely close timing of the firing-extraction cycle in the M14
since extraction begins before all the gas pressure has left the barrel,,,,the case still has not fully relaxed its grip on the chamber walls........... the result is case stretch when the bolt starts yanking the brass out ...
which results in bad (oversize) readings of the chamber dimensions
all fun stuff....
the only consideration I would have in how you are backing into the the proper chamber sizing is the potential for case neck stretch from the expander ball in the die...
with repeated sizing to get the shoulder right, you could be tugging at the case neck with the expander ball which might give an off-reading.
If the case is trimmed back to 2.005 and you get a good shoulder before it pulls/stretches beyond 2.015 you should be OK.
Also....keep in mind that you have sized and resized one piece of brass down to the dimension you want. The next fresh case you size may not behave the same way when run through the "adjusted" die just once.
If you want to get really deep into this you can have a chamber casting made and have one of the die makers machine a sizing die to your desired/exact dimensions
At the end of the day I simply cannot out-shoot most of the M14 types I have put together...they are always better than I'll ever be so I need to draw the line somewhere...or move over to rail-guns in 6ppc
That was in the days when I shot local matches. I would then use the RCBS case measurement gauge to get a numerical idea of my chamber dimensions and adjust my sizing die accordingly. Worked ok for my level of (non) proficiency
Sizing and/or measuring off an automatically-extracted case won't give you an accurate picture of the chamber due to the extremely close timing of the firing-extraction cycle in the M14
since extraction begins before all the gas pressure has left the barrel,,,,the case still has not fully relaxed its grip on the chamber walls........... the result is case stretch when the bolt starts yanking the brass out ...
which results in bad (oversize) readings of the chamber dimensions
all fun stuff....
the only consideration I would have in how you are backing into the the proper chamber sizing is the potential for case neck stretch from the expander ball in the die...
with repeated sizing to get the shoulder right, you could be tugging at the case neck with the expander ball which might give an off-reading.
If the case is trimmed back to 2.005 and you get a good shoulder before it pulls/stretches beyond 2.015 you should be OK.
Also....keep in mind that you have sized and resized one piece of brass down to the dimension you want. The next fresh case you size may not behave the same way when run through the "adjusted" die just once.
If you want to get really deep into this you can have a chamber casting made and have one of the die makers machine a sizing die to your desired/exact dimensions
At the end of the day I simply cannot out-shoot most of the M14 types I have put together...they are always better than I'll ever be so I need to draw the line somewhere...or move over to rail-guns in 6ppc
Yet another item to consider when you are trying to get a reading on any case fired through an M14 clone is that the ejector presses on one side of the case while the bolt-lugs rotate and the fired case begins to extract. When the bolt travels rearward the ejector is still pressing on three sides of of the still pliable just fired case(bolt lugs rotation). The case head/extraction groove isn't the same dimension all the way around to begin with then we combine that with the violent extraction of the burning hot case in an M14 clone and the problem becomes exponential. If you turn the same case 3 times in any tool designed to measure set-back you will get three different readings.
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Very true that is why fire-forming with the spindle shut to off will help you get a better case to work with, you removed the extraction variable
Thanks for keeping this going! I just returned from the range, and with my resized cases to 1.634, my performance improved somewhat. The best groups were produced with the Redding small base body die with a Redding bushing neck sizer, I took the advice I acquired here and didn't use the expander, the bushing is .335 for RA61 cases, which gives me a .3055 id neck. What I'm getting now is 2 holes, 2 rounds in one hole and 3 rounds in the other 1" apart going horizontally,out of five rounds. What I really noticed with the Redding SB die is it eliminated my first round flyer I always had with the FL dies. With these types of groups I maybe still sizing too small or my bedding is shot. Opinions? What I need I think is a difinitive headspace reading and size from there, mind you the bolt closes on a 1.638 case but not a 1.638 gauge, so the HS is probably closer to 1.636. I need to find out. The empties are 1.640. So would it be wise to size to 1.636 since brass tends to give more or I probably should play it safe with 1.634, I've read alot lately on this and its surprising how people differ on this, by some, I should be resizing to 1.638 and some say I should be resizing .002 under HS, so.....maybe it really doesn't matter that much, so just play it safe? Keep the opinions and suggestions coming!
I think the 2 shot group to the right has to do with the rifles recoil and placement after the first two shots. Since you are shooting a lot lately try this: Fire ten rounds into the same target. Between each shot take one minute and get up from the rifle...leave it lay there for an entire minute. Get back into position and fire again. I have noticed with a bbl having a RH twist I sometimes throw shots to the right usually my groups are strung low and right though...not too bad at 100 but they really drop to the right further out. I am a right handed shooter and during rapid fire I can actually feel the rifle slipping to the right and low. As for your dimensions I would cerrosafe the chamber like someone else in this thread mentioned...then I would measure the cerroform with the same instrument that you measure your sized cases with...and set the shoulder with from that cerrosafe(form) reading. Cerrosafe is extremely easy to use and nearly harmless to the user and entirely harmless for your rifle(s).
Thanks! I will cerrosafe, its seems easy enough. I could be dropping the right hand shots, I tend to set up prone with my body going left, so the rifle recoils more to the right, I will see, I am also going to try to shim the bedding per another gentlemans suggestion, I will post back soon, thanks again!
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